1. Field of the Invention
This invention relates to surgical instruments and is directed more particularly to an cannula.
2. Description of the Prior Art
Laparoscopy, a method for direct visualization of intra-abdominal contents is used as a means for evaluating abdominal pathology. Use of the laparoscope, in conjunction with a method of introducing instruments into the abdomen, permits these instruments to be manipulated under direct visualization and has thereby made possible the performance of various surgical procedures without a laparotomy.
Obstetrical procedures are particularly amenable to this method of investigation, especially exploratoy evaluation, tubal ligation by cautery or the Fallop ring, and cautery of endometriotic sites. All of the instruments required for such procedures can be passed through a narrow cannula and the procedure achieved as efficiently as with open manipulation.
The laparoscopic cannula procedure is as follows. A tubular needle connected to a low pressure carbon dioxide gas source is inserted through the umbilicus into the peritoneal cavity of the abdomen. This area is essentially the abdominal sac containing the viscera which must be evaluated or operated on. Carbon dioxide is instilled through the needle producing distension of the abdomen and expanding the anatomical space between the viscera and the abdominal wall. The needle is then withdrawn and puncture at the needle site is effected with trocar and cannula. The trocar is now removed and the laparoscope substituted by passing it through the cannula. Direct visualization of the abdominal contents is obtained.
In order to permit manipulation and/or operation within the abdomen, an additional puncture by a trocar and cannula at a second site is made. The trocar is withdrawn and introduction of various instruments such as probes, grasping forceps, cautery devices, or fallopian tube ring applicators may be accomplished through the second cannula while watching the procedure through the laparoscope disposed in the primary cannula.
Upon completion of the procedure, the secondary cannula is withdrawn, followed by the primary cannula and each puncture site is closed by a single stitch.
Cannulas in use today generally comprise a base member having a bore extending therethrough, and an elongated tubular metal member, or cannula tube, in alignment with the bore and extending outwardly from the base member. The base member is provided with a short tubular member, or seal mount, in alignment with the bore and extending in the opposite direction of the cannula tube. The free end of the seal mount is provided with a sealing member, usually of rubber or other elastomeric material, having a hole at its center. The cannula is ordinarily used initially in conjunction with a trocar -- an elongated sharp pointed metal device having a diameter which closely approximates the inside diameter of the cannula and having a hilt at one end. The trocar is pushed through the hole in the sealing member, passes through the base member, coming to rest with the trocar hilt adjacent the sealing member and the point of the trocar extending beyond the free end of the elongated cannula tube. In so doing, the elastomeric seal is maximally distended and frequently torn by the trocar's point.
In use, the trocar and cannula are, as a unit, driven through an abdominal wall distended by gas pressure, as described above. Once the cannula is in place the trocar has served its purpose and is replaced by an instrument, or number of instruments in series, most of which have a diameter smaller than that of the trocar so as to permit mobility within the cannula. Since the sharpened trocar has both enlarged and probably cut the elastomeric seal upon initial insertion, the seal achieved with instruments of smaller diameter is often inadequate, resulting in a persistent leak and consequent deflation of the abdomen. Therefore, it often becomes necessary to change the sealing member due to seal damage or an appreciable discrepancy in instrument diameter as compared to that of the precedent trocar.
During the change of the sealing member and/or instruments, the surgeon or his assistant must manually block the orifice of the exposed end of the cannula so as to minimize the loss of intra-abdominal gas. Such manual exertions are suboptimal inasmuch as the transition is awkward, usually permitting a goodly portion of the gas to escape through the cannula.
Another problem arises when an electrical cauterizing instrument is used in conjunction with the cannula. The instrument may contact the conductive metal tubular member and cause inadvertent singeing of the tissue surrounding the member.